bugfix: default floating border regression

Patch status: merged

Patch by Tony Crisci

Long description:

Fixes a bug where a normal floating default border is not applied when
the default tiling border is set to a pixel value.
This bug was introduced in this commit:
43b447855df095c56e860117d53acd0dd09ac42b
Consider motif border for floating geometry
Fixes a comment that claimed default floating border could override
motif hints, which was never the case.
fixes #1305